Well, this topic is of great interest to me, especially now that I have had a chance to work in the People's Republic and therefore have had a chance to observe the affect of diet in two cultures. My observations are anecdotal, so bear with me.
In China, people tend to be thin. The diet still mainly consists of rice, vegetables, meat (in small amounts), chicken and fish. The protein content varies from region to region. This type of diet seems to be accepted internationally as being healthy. Now, there is also a quickly growing middle class in China and along with that the money to "experience" Western food. McDonald's, KFC, Pizza Hut, etc. are everywhere in the larger centres. There is also a concern in China that middle-class people are getting fatter as a result. This is also influenced by fact that exercise is for kids or students. When you leave school you get married, have a family and work long hours. Of course, this also influences weight gain.
I got a real "eye opener" from one of my students. He was getting excited at the prospect of going to Canada for university and was perusing a picture book on Vancouver. He pulled me aside and showed me a picture of the Seawall in Stanley Park on a beautiful day. His question? Not, "Where is this?" or anything like that. He pointed to the people in the picture (of which there were many) and asked, "Are all people in Canada this fat?"